The invention relates to a filter for the gas flow of a gas generator equipped with a gas-producing propellant charge, the filter consisting of a woven netting, of a knitted netting or of a grid and being arranged inside a filter chamber.
On the basis of the German Published Unexamined Patent Application (DE-OS) 25 38 386, the use of woven wire nettings or knitted wire nettings has become known for filter inserts of airbag gas generators.
It is customary to use a winding of strips of woven wire netting for the filter which has an approximately rectangular cross-section. This winding is pressed and inserted into the filter chamber. However, since the cross-section of the filter chamber is not rectangular, but has radii in its contour, there are several resulting disadvantages: On the one hand, the available volume is not utilized and, on the other hand, difficulties occur during the mounting of the individual housing parts of the gas generator because of the high firmness of the wire winding. Finally, there is the important secondary effect that the gas jet coming out of the combustion chamber, in an unhindered manner, strikes the wall of the filter chamber consisting of aluminum and in the process removes material out of the wall and burns it. On the one hand, this influences the burn-up behavior of the gas generator and, on the other hand, holes may be burnt into the exterior wall through which the gas jet emerges.
It is an object of the invention to design a filter for an airbag gas generator, the housing of which may, for example, consist of aluminum and which avoids the above-mentioned disadvantages.
This object is achieved according to the invention in that the filter consists of a gas-permeable material with a large effective surface which completely fills up the filter chamber. A circular wire knit is preferably used for this purpose which, after being cut into lengths, is rolled up and is pressed into a shape corresponding to the filter chamber. An open-pored foam or a foam-type material is also suitable for this purpose, according to other contemplated embodiments of the invention.
The special advantages of the filter according to the invention are, on the one hand, that in the filter which fills up the filter chamber, the gas has a diffusely dispersed flow and therefore no longer acts in a punctiform manner on the outer wall. On the other hand, the efficiency of the filter will increase because empty spaces without any filter material are avoided inside the filter chamber. Finally, in addition to the advantage of avoiding incorrect mountings of housing parts which concerns the manufacturing process, there is also the economical advantage of a considerably lowerpriced manufacturability of the filter.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.